Experience with metal-filled Teflon seats

[moltenmetal]

Hi All- just wondering if anyone has documented experience, good bad or ugly, with ordinary (i.e. not trunnion type) 3-piece ball valves using 50% stainless steel or nickel powder-filled Teflon at temperatures above the normal upper service limit of reinforced Teflon, which I would put at around 232 C (450 F). Several valve manufacturers are selling these seats as a low torque alternative to PEEK for middle temperature applications, some stretching the service to 260 C (500F) and some stretching it even further to 550 F for low pressure services. Others are stretching similarly filled Teflon seat materials, where the filler is carbon or something other than glass. I'm suspicious...and the only people I have telling me that the valves are actually reliable at these operating fluid temperatures, aside from the people who wrote the datasheets of the valve manufacturers, are the salesmen.

What I'm interested in is services where the actual fluid temperature was consistently above 450 F, not services where the valve was used merely to stretch the design margin to a higher temperature. Service conditions (approximate) and fluid being handled would be of interest, as well as whether or not the valve was heat traced externally or just insulated.

 

[mbelly84]

hi moltenmetal, what valve size / pressure rating are you talking about? are they manual or actuated valves?
i honestly don't have any experience on this metal filled PTFE seats, but at that temperature, i'd just go with PEEK.
if they are low pressure / small valves, which i think they are considering that are floating balls, you won't have big disadvantages in terms of torque.

 

[moltenmetal]

Valves are small, 1/2" through 2", and actuated. Yes, this is a normal floating ball valve design, and yes you do need to go significantly bigger with the actuator for PEEK seats rather than these metal-filled Teflon ones- again, trusting the manufacturer's datasheet. We have plenty of experience with PEEK already so know that to be an acceptable alternative.

What I'm after is actual service experience with these seats at temperatures above which I've been taught to trust teflon. I just don't believe they could last, but the advantages are fairly significant if they do- and I can't use any of my clients as a guineapig to test them out.

The one mfg rep/salesman is fairly trustworthy, so I'll see if I can get some client references from him- but would prefer to know if anybody here has service experience with them that they can share.